/Engine/Source/Runtime/Engine/Public/Net/OnlineEngineInterface.h
Login a local user to the online subsystem before starting a Play In Editor (PIE) instance, using credentials stored in the editor
virtual void LoginPIEInstance ( [FName](API\Runtime\Core\UObject\FName) OnlineIdentifier, int32 LocalUserNum, int32 PIELoginNum, FOnPIELoginComplete & CompletionDelegate )